Bleeding disorders or coagulopathies, a group of conditions characterized by abnormalities in the blood coagulation process, are associated with increased mortality and hospital length of stay following acute trauma, illness and surgery. Coagulopathies could result from multiple pathological, inheritable, trauma-induced or transfusion induced conditions, causing) hypercoagulable or hypocoagulable states that may endanger life. The coagulopathy also occurs rather frequently following an acute trauma and hemorrhage in patients. Trauma-induced coagulopathy is often the underlying cause of uncontrolled internal bleeding and, according to some accounts, leads to up to a fivefold increase in patient mortality. In order to normalize blood coagulation condition, a hemostasis therapy is essential that includes transfusion of whole blood or tissue factor concentrates. An early detection of the coagulopathy in patients and monitoring of coagulation metrics during the hemostasis therapy to guide therapeutic end-points is important and, at the same time, currently problematic partly because of the long turnaround time of standard laboratory-based coagulation testing methods.
Thromboelastography (TEG) or rotational thromboelastometry (ROTEM) is a tool used to determine blood coagulation status by measuring changes in the material properties of a blot clot during the coagulation process. In a TEG approach, a sample of whole blood is placed within a sample holder such as an oscillating cup, for example, a shaft is immersed in the sample, and changes in mechanical torque induced on the shaft during blood coagulation are measured to provide data representing processes of initiation and formation of a blood clot and its firmness. While the TEG provides a tool for coagulopathy assessment, at least two considerations currently limit the application of the TEG modality for point of care settings. Firstly, the blood-clot assessment in the TEG is based on the measurement of torque resulting from mechanical resistance of the bulk volume of the sample being measured. Additionally, the TEG does not necessarily afford sufficient sensitivity to detect minute local heterogeneities during microscopic clot formation during the initial stages of clot initiation and progression. However, the initiation of the coagulation process may be important for diagnosing early coagulopathy in patients that may be left undetected by the TEG approach. Secondly, the instrumental complexity of calibration and mechanical torque measurements poses a practical challenge to reliable and rapid use in a point of care setting, thereby limiting the applicability of the TEG in field settings.
Point of care and laboratory devices that can provide rapid coagulation assessment over the entire coagulation cascade are critical in guiding and monitoring hemostasis therapy and determining therapeutic end-points. There remains a need, therefore, for systems and methods for characterization of blood coagulation that are sufficiently versatile to overcome the deficiencies of the currently used technique.